How should a pleural effusion that develops after open‑heart surgery be evaluated and managed?

Management of Pleural Effusion After Open Heart Surgery

Intervene with ultrasound-guided thoracentesis only when the effusion is symptomatic (dyspnea, increased respiratory support, cough, tachypnea, or pleuritic pain) AND either occupies >25–33% of the hemithorax or exceeds 400–480 mL in volume; asymptomatic effusions should be observed regardless of size. 1

Understanding Post-Cardiac Surgery Effusions

Prevalence and Natural History

• Pleural effusions develop radiographically in 42–89% of patients after cardiac surgery, but only 6.6% require therapeutic intervention 2
• The vast majority follow a benign, self-limited course without affecting mortality 2
• Approximately 21% of drained effusions recur despite initial intervention 2

Temporal Classification and Fluid Characteristics

Early effusions (≤30 days post-surgery):

• Characteristically exudative with elevated erythrocyte counts, elevated LDH, and eosinophilia 2, 3
• Reflect direct surgical trauma, bleeding, and pleural inflammation 2, 3

Late effusions (>30 days post-surgery):

• Predominantly lymphocytic with lower LDH levels 2
• Suggest an immune-mediated process rather than surgical trauma 2

Clinical Assessment Algorithm

Step 1: Determine Clinical Significance

The effusion is clinically significant if ANY of the following are present:

• Increased need for respiratory support 2
• Dyspnea or shortness of breath 2
• Cough or tachypnea 2
• Pleuritic chest pain 2

If asymptomatic: Observe regardless of effusion size—no intervention needed 2, 1

Step 2: Radiographic Sizing

• Use chest radiography to classify as small (<25% hemithorax), moderate, or large (>25–33% hemithorax) 2
• Ultrasound provides superior sensitivity for detecting fluid and identifying features suggesting complication (loculations, septations, echogenic debris) 1, 4

Step 3: Apply Intervention Thresholds

Drain the effusion when BOTH criteria are met:

• Patient is symptomatic (see Step 1) AND
• Volume exceeds 480 mL (reduces hospital stay by 3±1.5 days vs. diuretics alone) 2 OR
• Volume exceeds 400 mL OR any volume with symptoms (improves walking distance and recovery by up to 15%) 2

Drainage Technique and Safety

Preferred Method

• Ultrasound-guided thoracentesis is first-line, replacing surgical tube thoracostomy 2, 1
• Ultrasound guidance reduces pneumothorax risk (blind thoracentesis carries ~19% pneumothorax risk) 1

Volume Limits

• Remove 1–1.5 L maximum per session to prevent re-expansion pulmonary edema 1

Fluid Analysis

Routine studies on all diagnostic thoracenteses:

• Gram stain, culture, cell count with differential 4
• Protein, LDH, pH 4
• Cytology 4

Additional testing when indicated:

• Triglycerides if chylothorax suspected (milky appearance, thoracic duct injury) 2, 5
• Tuberculosis testing in high-prevalence regions 4

Specific Complications Requiring Urgent Drainage

Infected Effusion (Empyema)

Drain immediately if ANY of the following:

• Frank pus on aspiration 1
• pH <7.2 1, 4
• LDH >1000 IU/L 1
• Glucose <60 mg/dL 1

Hemodynamic Compromise

• Hemodynamic instability or tamponade physiology warrants immediate diagnostic and therapeutic thoracentesis 1

Adjunctive Medical Management

Post-Pericardiotomy Syndrome

• First-line: NSAIDs for symptomatic relief 2
• Preventive therapy: Colchicine postoperatively reduces syndrome incidence 2, 6

Fluid Management Optimization

• Use buffered crystalloids (Ringer's lactate or acetate) instead of 0.9% saline 1, 6
• Target conservative positive fluid balance of 1–2 L by end of operative case; reduce further when effusion present 1, 6
• Avoid albumin and synthetic colloids—these increase bleeding, re-sternotomy, and infection risk without improving outcomes 6

Critical Pitfalls to Avoid

• Never drain asymptomatic effusions—this exposes patients to procedural risk (pneumothorax, bleeding, infection) without clinical benefit 1
• Never perform blind thoracentesis—always use ultrasound guidance 1
• Do not rely on exudative vs. transudative distinction alone—nearly all post-cardiac surgery effusions are exudative by Light's criteria, but most are benign and self-limited 3
• Do not use hydroxyethyl starch or routine albumin—these worsen outcomes in cardiac surgery patients 6
• Do not delay drainage of infected effusions—pH <7.2 mandates prompt catheter or chest tube drainage, possibly with tissue plasminogen activator/DNase therapy 1, 4

Follow-Up Considerations

• Late effusions (>30 days) require comprehensive investigation before attributing to postoperative cause, as literature on late effusions is sparse 2
• Protocolized follow-up with standardized drainage criteria improves recovery rates and reduces hospital length of stay 2